MOERISON 



MORRISON; Yes, up to the size of a rabbit. 



HART: Are these all good regulators? 



MORRISON: We did not do exhaustive studies of regulation, but 

 they seemed to regulate well. 



HART; With five degrees of cooling do they always double the 

 heat product? 



MORRISON: Yes, for all the mice and rats. And incidentally, in 

 a regime like this it is desirable to have knowledge of "where you 

 are going," so that the cold exposure is not too prolonged. Knowing 

 the animal and the previous experience one can approach the critical 

 oxygen pressure quickly. 



HART; Your critical temperature was quite high in all of them, 

 I gather from this. 



MORRISON: Yes, it was in relation to their size and insulation. 



PROSSER: Did you find any differences between the sea level and 

 the altitude population of the Phy lotus? 



MORRISON: By this index, yes, very definitely. 



PROSSER: Is there any evidence that this is genetic? 



MORRISON: Yes. We took high-altitude mice to sea level. They 

 bred there and bore the litters which were raised to adults. The per- 

 formance of these "low- raised" mice approached that of the parents. 

 They had spent their entire lives at sea level and yet they were phys- 

 iologically high-altitude mice. 



JOHANSEN; In your many curves of the body temperature plotted 

 against ambient temperature, it seems inevitable to me that the 

 curve must bear some relation to the time of exposure to these tem- 

 peratures, particularly below the critical temperature for the 

 species. 



416 



